Childhood sunburns ‘important contributor’ to melanoma, cSCC later in life
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Sunburns early in life may be associated with melanoma or cutaneous squamous cell carcinoma later in life, according to a study.
“To our knowledge, no study investigated lifetime patterns of sunburns and skin cancer risk, likely because understanding the relationship between sunburns over a lifetime and skin cancer risk is challenging,” Simon Lergenmuller, PhD, of the department of clinical and registry-based research at the Institute of Population-Based Cancer Research, Cancer Registry of Norway, told Healio.
“Past sunburns may affect behavior in relation to sun exposure, in turn affecting future sunburn frequencies, making it difficult to investigate the association between sunburns at different ages with skin cancer risk,” he said.
In the population-based cohort study, Lergenmuller and colleagues identified lifetime trajectories of sunburns to determine whether differing trajectories could impact cutaneous melanoma and cutaneous squamous cell carcinoma (cSCC) risk.
“By looking at lifetime patterns of sunburns and their relationship with skin cancer, we can better understand how to prevent these skin cancers,” Lergenmuller said.
Eligible participants were culled from the Norwegian Women and Cancer Study. Data from 1991 to 2018 were included, with questionnaires administered every 5 to 7 years between 1991 and 2007.
“To our knowledge, only one cohort study has investigated the association between sunburns and both melanoma and cutaneous squamous cell carcinoma risks, though timing of sunburns was not assessed,” Lergenmuller said. “Our goal was to overcome these challenges and expand the current knowledge using the large population-based Norwegian Women and Cancer cohort study linked to the Cancer Registry of Norway.”
Exposures of interest included pigmentation factors, sunbathing vacations and indoor tanning, along with the frequency of sunburns occurring from childhood through adulthood.
The researchers evaluated completed questionnaires from 169,768 women aged 31 to 70 years that contained information about sunburns. They stratified the lifetime trajectory of sunburn frequency into five groups from low to high or vice versa. The trajectories had age ranges up to 39 years (n = 159,773) , 49 years (n = 153,297) or 59 years (n = 119,170).
The mean follow-up duration was 14.3 to 19.5 years. In that time, 1,252 to 1,774 women were diagnosed with incident primary melanoma, while 739 to 871 women received diagnosis of incident primary cSCC.
Compared with those with a stable low trajectory of sunburn frequency, participants with a stable high frequency aged up to 39 years were at greater risk for both melanoma (HR = 1.5; 95% CI, 1.28-1.75) and cSCC (HR = 1.51; 95% CI, 1.22-1.87). In similar comparison with the stable low trajectory group, those aged up to 39 years with high to low trajectories also were at increased risk for melanoma (HR = 1.44; 95% CI, 1.2-1.73) and cSCC (HR = 1.47; 95% CI, 1.14-1.91).
“Our results showed that sunburns in childhood were the most important contributor to melanoma later in life and avoiding those is crucial,” Lergenmuller said. “High frequencies throughout life also showed increased risk. Our results therefore emphasize the importance of avoiding the sun, seeking shade, using protective clothing and sunscreen throughout life.”
Other trajectories failed to show such significant risks for malignancy, according to the findings. In addition, no statistically significant heterogeneity was observed for melanoma and cSCC estimates, according to the study.
“The literature suggests that the development of melanoma and squamous cell carcinoma are related to different types of exposure to the sun. While intense and intermittent sun exposure is considered the strongest risk factor for melanoma, chronic and cumulative sun exposure is more related to squamous cell carcinoma,” Lergenmuller said. “It was therefore surprising that we did not find any significant differences between the estimates for these two skin cancers. Meaning, the different types of sunburn trajectories identified increased both melanoma and SCC risk in the same way.”